Fluid operable control device



Dec. 3l, 1946. R. J. BusH FLUID OPERABLE CONTROL DEVICE FledSept. 2Q,1944` 2 Sheets-Sheet l Dec. 31, 1946.

Fig

R. J. BusH 2,413,287

FLUID OPERABLE CONTROL DEVICE Filed sept. 29, 1944 2 sheets-sheet 2ATTaRA/EY Patented Dec. 31, 1946 FLUID OPERABLE CONTROL DEVICE Rankin J.Bush, Jeannette, Pa., assignor to The Westinghouse Air Brake Company,Wlmerding, Pa., a corporation of Pennsylvania Application September 29,1944, Serial No. 556,406

9 Claims.

This invention relates to control devices and more particularly to thetype adapted to be controlled and operated by fluid under pressure.

In my copending application Serial No. 480,161, filed March 23, 1943,and assigned to the assignee of the present application, there isdisclosed a fluid pressure control system for controlling a plurality ofinternal combustion engines, such as employed for propelling anairplane. This system embodies a plurality of fluid motors for eachengine, one motor for controlling the engine speed, another the richnessof the fuel mixture supplied to the engine, another for controlling thetemperature of the mixture, and still another for controlling theoperation of a blower or supercharger. Y

One object oi the invention is the provision of an improved fluid motorfor controlling operations such as above described.

Another object of the invention is the provision of an improved fluidmotor embodying fluid pressure adjustable pilot means and power meansadapted to be operated by fluid under pressure for adjusting the devicebeing controlled, the pilot and power means cooperating to insurepositive operation of the power means and thereby adjustment of thedevice in accordance with the adjustment oi the pilot means.

Another object of the invention is the provision ci a motor such asabove described arranged to employ a single pipe for controllingoperation of the pilot means and for providing fluid under pressure forcontrolling operation of the power means, so as to maintain at a minimumthe weight of the apparatus.

Another object of the invention is the provision of a fluid motor suchas above defined which is so constructed as to render the pilot portionvery sensitive to and adjustable in accordance with slight changes in acontro-lling fluid pressure, and which also renders the power meansaccurately and positively adjustable in accordance with the adjustmentsof the pilot portion.

Another object of the invention is the provision of a fluid motor of theabove type which is relatively small in size; compact and simple inconstruction, and light in weight for the purpose intended.

Other objects and advantages will be apparent from the following moredetailed description of the invention.

In the accompanying drawings:

Fig. l is a longitudinal sectional view, partly in diagrammatic form, cione embodiment of the lio invention; and Fig. 2 is a View similar toFig. 1 of a modied form of the invention.

Description, Fig. 1

The improved fluid motor shown in Fig. 1 of the drawings comprises ahollow casing section I open at one end and having at the opposite end awall 2 and a sleeve 3 carried by said wall and extending centrally intoa cylindrical chamber 4 formed within said casing section. The open endof the casing section I, and thereby of chamber Il, is closed by a cover5 secured to the casing section I by securing means 6, and clampedaround its peripheral edge between said cover and casing section is aflexible diaphragm 7.

One side of diaphragm 'l is subject to pressure of fluid in chamber 4which is open to a fluid pressure release pipe 8. The pipe 8 may leaddirectly to atmosphere, or it may lead to a socalled sump reservoir (notshown) which is used in connection with certain fluid pressure controlsystems for receiving fluid under pressure after it has been used toeect a desired operation. In such systems the fluid pressure released tothe sump reservoir is recompressed for reuse. This is immaterial to thepresent invention and no further description of the sump reservoir forits function is therefore necessary, although if desired, referencemaybe made to my copending application hereinbefore referred to for acomplete disclosure of a fluid pressure control system embodying a sumpreservoir such as above mentioned.

At the opposite side of diaphragm "I, and thus between said diaphragmand the cover 5, is a uid pressure control chamber S which is connectedthrough a port I to a cavity I I in said cover. The cavity II is openthrough an air strainer I2 to a pipe I3 which is connected to the cover.The pipeV I3 constitutes a combined control pipe and fluid pressuresupply pipe, as will be more clearly brought out hereinafter.

The uid motor further comprises a power cylinder portion I4 which issecured by securing means I5 to the opposite end of casing section I,that is, to the end wall 2, a sealing gasket `I6 being clamped betweenthe two parts to prevent leakage of fluid under pressure through thejoint. This portion I4 and the cover 5 are provided with bosses II forcontact with a mounting plate of the like (not shown) and said bosseshave screwthreaded bores I8 for receiving the threaded portionsof capscrews or the like (not shown) to secure the motor in a desired locationor position.

`The power cylinder Ill contains a differential area piston means i9,which for the purpose of illustration only, may comprise two axiallyarranged, spaced apart and connected piston heads 25 and 2l; the pistonhead 2E! being of greater diameter than the piston head 2i. These pistonheads are slidably mounted in suitable bores in the power cylinder I4and each head is provided with a ring groove in which there is disposeda ring 22 having sealing and sliding Contact with the Wall of therespective bore.

One end of the bore in which the larger piston head 2li is disposed isclosed by wall 2 of the casing section I, and said wall together withthe adjacent face of the piston head form a fluid pressure controlchamber 23. The opposite end of the bore, in which the piston head 2| ismounted, is closed by an end wall 24 of the power cylinder I4 andbetween said end wall and the adjacent face of the piston head is achamber 25 which is open to atmosphere through a port 25. Between thetwo piston heads 20 and 2I is a dash-pot chamber '2l' which is inconstant communication with the combined control and fluid pressuresupply pipe I3 by way of a passage 28, containing a choke 28a, a passage25, a pipe 30, and a passage 3i in the cover 5, leading to cavity IIwhich is connected to pipe I3. It will be noted that the opposite ends fpipe 38 are, respectively, disposed in recesses in the cover andcylinder portion I4, and are engaged by sealing rings 32 to preventleakage of fluid under pressure from said pipe to atmosphere.

The piston means I9 is arranged in coaxial relation to the openingthrough sleeve 3, which opening is lined for a portion of its lengthadjacent its inner end with a wear bushing 33. The piston means I9 has astem 34 projecting therefrom through the sleeve 3 and bushing 33. Withinthe bushing 33 the stem 34 has a piston portion 35 of substantially thesame diameter as the bore of the bushing and this piston portion carriesa ring 35 having sealing and sliding contact with the inner wall of saidbushing. At both sides of the piston portion 35, the stem 34 is ofsmaller diameter than the bore in bushing 33, and this provides, at theside adjacent piston means I9, an annular space 37 around the stem 34,which space leads and opens to the uid pressure control chamber 23.

A rod or stem 38-arranged opposite the stem 34 projects from the pistonmeans I3 through chamber 25 and a bore in a boss 39 projecting from theouter face of the end wall 24 of the cylinder portion I4 of the casing.In the b oss 33, adjacent its outer end, is-a wear bushing 4D in whichthe rod 33 is slidably mounted and supported. Adjacent the inner end ofbushing 4Q is a ring 4I secured in boss 39 and having sealing andsliding Contact with piston rod 33. Between the ring 4I and the bushing4I] there is a groove 42 encircling the rod 38 andadapted to carrylubricant for lubricating saidV rod. The means by which groove 42 islled with lubricant is not shown in the drawings and is immaterial tothe invention. At the opposite end of bushing is a ring 43 havingsealing and sliding contact with the piston rod 38 and this ring is heldin place in boss 39 by any suitable securing means, such as a snap ring44. The two rings 4I and 43 act to prevent leakage of lubricant alongthe piston rod from groove 42, as will be obvious.

The piston rod 3S also projects through an opening provided in a boss`45extending into chamber 25 from the end wall 24 of the cylinder portionI4. Adjacent its inner end the boss 45 4 is in substantial contact withthe peripheral surface of rod 38 and is provided with an annular groovein which there is disposed a ring 46 having sealing and sliding contactwith the rod. Between the sealing ring 46 and the sealing ring 4I, theboss 45 has a recess or chamber 4l encircling the rod 38 and to which isopen or connected the passage 29, which, as before described, is open tothe combined control and fluid pressure supply pipe I3. The sealingrings 4I and 46 are provided to prevent leakage of fluid under pressurein either direction along the rod 38 from chamber 4T.

Beyond the end of boss 39, the end of the piston rod 38 is disposed in aslot 50 provided in an operating lever 48 between the ends of saidlever, said rod being operatively connected to said lever by a pin S9extending through aligned openings in said stem and the opposite sidewalls of slot 5U.

The lever 43 has at one end a rib 5I provided with a surface 52 arrangedgenerally parallel to the length of the lever and at an angle to theaxis of the piston rod 38. A fulcrum member 53 is mounted against thissurface 52 and has a stud 54 extending through a slot 55 in rib 5I, saidslot extending parallel to the length of the lever. A lock nut 55 onstud 55 is provided to contact the side of rib 5l opposite surface 52 tosecure member 53 in an adjusted position with respect to said surface.Release of nut 55 from rib 5I will permit adjustment of member 53 onsurface 52, as will be apparent.

For adjusting the fulcruin member 53 along the surface 52, an adjustingscrew 51, extending i parallel to the length of the lever and through abore in said member, has screw-threaded engagement with said member.This adjusting screw extends through a slot 58 provided in a rib 59extending from the rib 5I. On the outer end of screw 5? is a head Si)engaging the outer surface ofrib 5S. The head 50 is provided with a slot6i to receive a screw driver for turning the screw. Adjacent the innersurface of rib 59, a washer 62 is disposed in an annular groove in thescrew 5l, said washer and the screw head 50 being thus arranged tocooperate with the rib 59 to hold the screw 5l against longitudinalmovement relative to the lever, whereby the member 53 may be adjustedeither toward or away from the piston rod 38 by turning the screw Sli-Turning the lock nut 56 against rib 5I will lock the member 53 in anadjusted position.

The member 53 is connected by a pivot pin 63 to one end of a link 64,the opposite end of which link is mounted to turn on a pin 55 secured inan ear S6 projecting from the cylinder portion I4 of the motor.

The opposite end of lever 43 is adapted to be connected to a devicewhich it is desired to operate and for this purpose may be provided withone or more openings 61 either one of which is adapted to receive aconnecting pin of the like.

Between the holes 61 and operating pin 49 the lever is provided with abore in which is mounted an adjusting screw 68 having screw threadedengagement with the wall of said bore. The inner end of screw 68 engagesa shoulder 69 on the cylinder portion I4 of the motor, while in theouter end is a slot 'I0 for receivinga screw driver whereby the screwmay be turned. A lock nut lI on the screw 68 is provided to engage thelever to lock said screw in an adjusted condition.

Disposed in chamber 4 is a diaphragm follower 'I3 comprising a centralcylindrical portion 14 which at the end opposite the diaphragm 'l isprovided with an annular inturned flange 15, and

an annular outturned ange 16. A coil regulating spring 11 contained inchamber Il and encircling the sleeve 3 projecting from end wall 2 of thecasing section I, has one end bearing against said wall and the oppositeend bearing against the ange 19. This spring is under pressure, forreasons which will be later brought out.

The end of the cylindrical portion 14 of follower 13, adjacent todiaphragm 1, is closed by a cap 18 having as its center an aperture, andfreely extending through this aperture into a chamber 19 formed withinsaid cylindrical portion is a boss 89 which is formed integral with thediaphragm 1. The diaphragm and boss 88 are both preferably made of aresilient material, such as a rubber composition.

The diaphragm 1 comprises a central portion engaging the cap 18, anannular clamping flange 8| disposed between the casing section I andcover as before mentioned, and a connecting annular corrugation 82 theinner wall of which is telescoped over the central portion 18 of thefollower 13 for supporting said follower. In this supported relation ofthe diaphragm follower 18 relative to the diaphragm, the boss 89 is freeof contact with the cap 18.

A boss -83 projecting into chamber 9 from cover 5 is provided forcontact by diaphragm 'l to limit deflection of said diaphragm in thedirection of said cover by spring 11. A rib 88 projecting from wall 2 ofthe casing section I into chamber 23 is provided for contact by pistonmeans I9 to limit movement of said piston means in the same direction.

A valve member 85 contained in chamber 8 has a collar 86 engaging theend of the piston stein 34, and also has a portion 81 extending into abore in said stem. Adjacent collar 88 the portion 81 is provided withscrew threads cooperating with threads in the stem 34 to secure themember 85 to said stem. Beyond this screw-threaded portion of member 85the stem 34 is provided with an annular recess 88 encircling said memberand connected by port 89 to the annular space 3i' which encircles thestem 34 and which is open to the control chamber 23 at the right handface of the piston head 28. The port 89 is of relatively small size andacts in the capacity of a choke and may hereinafter be referred to aschoke 89.

The piston stem 88 has a chamber 98, one end of which is formed by theend of the portion 81 o-f the valve memb`er 85. Leakage of fluid underpressure between chamber 98 and recess 88 is prevented by a ring 9|carried in a recess in stem 34 and engaging the peripheral surface ofsaid portion 81. The chamber 98 is in constant communication with thecontrol and fluid pressure supply pipe I3 by way of an axial bore 92extending through the piston means I9 and into the piston stem 38 whereit is connected by a radial port 93 to the annular recess 41 encirclingsaid stem.

The valve member 85 also has a part 94 extending into chamber 19 in thecylindrical portion 18 of the diaphragm follower 13. In chamber 19 thepart 94 is provided with an annular collar 95 which is of greaterdiameter than the opening through flange on the diaphragm follower andwhich is adapted to be engaged by said flange under a condition to belater described.

The valve member 85 has an axial bore which opens at one end to chamber98 through a valve seat provided for engagement by a fluid pressuresupply valve 99 contained in saidl chamber, and

which opens at the opposite end through the bottom wall of a counterbore provided in the part 94 of said member. Slidably mounted in thiscounter bore is a cup shaped retainer 91 having a bore through itsclosed end aligned with the bore in member y85. Extending through thisbore in retainer 91 and into the bore in valve member is a sleeve 98adapted to reciprocate in said bores. The sleeve 98 has an enlargementor head 99 partially contained within the retainer 91 and adapted to beengaged by boss 88 projecting from the diaphragm. Encircling the head 99is an annular collar |88, and interposed between this collar and theclosed end of the retainer 91 is a coil spring |8I which encircles saidhead and is under compression. One purpose of this spring -is to urgethe retainer 91 against one side of a sealing ring |82, which iscontained in a recess in Valve member 85 encircling the sleeve 98, forthereby forcing said ring into sealing and sliding contact with saidsleeve to prevent leakage of uid under pressure from the inner end ofsaid sleeve along the outer surface of said sleeve and past saidretainer to chamber li.

The sleeve 98 has an axial bore |83, one end of which is connectedwithin the head 99 to a re1- atively small port or choke |84 which opensto chamber 19 within the diaphragm follower 14 and .thus to chamber 4an-d Ithe uid pressure release pipe 8. The opposite end of bore |83opens through a valve seat on the opposite end of the sleeve to theaxial bore in valve member 85, and slidably mounted in said axial boreis a pin |05 having on one end a release valve |86 disposed for engagingsaid valve seat. The pin |85 is integrally connected by a iiuted s-tem|81 to the supply valve 96. The iiuted stem |81 has slid-ing ,contactwith the wall of the bore in which it is disposed, while the pin |85 isof smaller diameter than said bore. Between the supply valve 96 andrelease valve |89, the axial bore in the valve mem- .ber 85 i-sconnected by a radial por-t |88 to the annular recess 88 encircling saidmember.

A spring seat I 89 is disposed in the supply valve chamber 98 against ashoulder formed at the .junction` of said chamber and bore 92, andinterposed between and engaging at opposite ends said seat and thesupply valve 98 is a coil spring II8. This spring is under pressure andconstantly eifective to urge the supply valve 96 and release valve |86inthe direction of their seats. The spring seat |89 `is provided with abore III connecting the supply valve chamber 98 to bore 92.

Adjustments, Fig. 1

Assuming that -the pressure of the fluid at the source (not shown) forsupply through pipe I3 to the fluid motor is pounds and that .thedesired range of variation in pressure of fluid for controllingoperation of said motor is seventy pounds, the difference, or eightypounds, may be the minimum pressure, or what may be considered as thenormal pressure, provided in pipe I3 Ito the motor by operation' of anoperators control device (not shown).

This normal pressure of fluid in pipe I3 will equalize through port I8into diaphragm chamber 9, and also through port 3 I, pipe 38, passages29 and 28 and choke 28a into .the dash-pot chamber 21 between the twopiston heads 28 and 2|, and will also equalize into the supply va-lvechamber 98 from passage 29 by way of annular chamber 41 encircling thepiston -r-od 38 and port 93 and bore 92 in said rod.

The normal pressure of eighty pounds effective -in diaphragm chamber'ilonthe diaphragm-82 vwill deflectsaid diaphragm againstthe opposingvnormal position of the diaphragm is theposition in which-it is shown inthe drawings, but it will be understood that for-different springs 'I'I.the normal position may be either slightly to one-side vor the other ofthe position in which the diaphragm is shown in the drawings.

`The normal pressure of fluid efiective inthe dash-pot chamber 21be-tween the piston headsiZIl and 2| produces a force, equal to saidpressure times the diierence in areas of the two piston heads, and thisforce acts to move the piston means I9 and all parts Ysecured theretooricarried thereby in the direction of the right hand. The adjusting screw68 may initially be backed out of the lever 48 sufiiciently to permitthepiston means I9 to move the head 99 on the release valve sleeve-98 intocontact with boss 80 on Vthe .diaphragm I andto then move the valvemember 85 relative to said sleeve. As the valve member 85 is thus movedrelative to sleeve 9S the release valve |06 will be moved by spring I|0into seating .engagement with the end of the sleeve 98. The sleeve 98,being held against movement by contact with the diaphragm boss 80, willthen hold the release valve |36, as well as the supply valve 9B, againstfurther movement with valve member 85. Asa result, the continuedmovement of the piston means I9 and valve member 85 by pressure of fluidin dash-pot chamber 21 Ywill move said member out of seating engagementwith the fluid pressure supply valveg.

When the supply valve'96 is thus opened, fluid under pressure, suppliedto the supply valve chamber 90 from pipe |3,-will then flow past saidvalve and through ports |08 and 89 to chamber 23 at the right hand faceof the larger piston head 20 and therein produce a force against saidhead which acts in opposition .to the opposing force created by pressure-of huid in chamber 21 between the two piston heads. sure will thuscontinue to be supplied to chamber 423 until the force created thereby,slightly eX- ceeds the opposing force created by pressure of iluid inchamber 2T whereupon the piston means I9 will start to move in thedirection of the left hand and will continue such movementA until thevalve `membere seats against the supply valve S6 and prevents furtheriiow of uid under pressure to chamber 23. When the supply of-fluid underpressure to chamber 23y is thus cut off, itA Will be noted that thepiston means i9 Will cease moving in a position in which both` thesupply and release valves will be closed, and fluid at some pressure,such as forty pounds, will be effective in chamber 23 balancing theopposing pressure of iluid in chamber 21 on piston means I9.

After the piston means I9 attains'the normal position determined by themini-mum pres-sure of fluid (eighty pounds) in pipeV I3, the screw 8 isthen turned into contact with shoulderfl on the .casing which thereafterwill define the'normal position of lever-48.

The pressure pickup characteristic of springV 'I1 determines the extentof deflection of diaphragm v'|,ias above mentioned. It-will thereforebeap- Fuid under pl'esparent'that whensaid "diaphragm isjsubjected to-a'maximum pressure, Vtheextent of deflection of said Vdiaphragm lfrom Yits normal position will be less if the pickup of'the spring I1-isrelatively great than if thepickup is less. The movement of piston meansIiQcorresponds to the deflection of the diaphragm, as will hereinaftervbebrought out, and thus also depends Aupon the 'pickup of controlspring 11.

Regardless of thepressure increase'orpickup characteristic of lspringA1l however, Vit is desired to provide a certain range of movement ofthe opleratingleverA 48, ateither oneor the other of the openings-fil towhich the'device tobe controlled will be connected-and this'is obtained'by adjustment of the'lever fulcrum member 53 'relative to the lever 48by means of the screw.5'|. Forinstancefif the pickup of spring 'I1 isrelatively vgreat,thereby Vlimiting `the deflection of (diaphragm '1,thefulcrum member 53 will be adjusted toward the pin -49 to increase themovement of the lever at the one or other opening 81. On the other hand,if the pickup of the spring is less, so that the diaphragm 'I willbedeflected to a greater extent for a certain change in pressure of uid inchamber 9, the fulcrum member 53 will be adjusted away from pin 49 toreduce the movement of lever 58.

It Will now be seen that the pickup characteristic of spring ildetermines the normal position of diaphragm "I and Vthereby of vpistonmeans I9 and lever 48, while adjustment of the lever fulcrum member 53relative to said lever provides for obtaining achosen `degree ofmovement of said lever, at the point where it will be connected to-thedevice being controlled. liet it be assumed that the desired range ofmovementof lever 48 is between the position'in -which it is shown in thedrawing and a position such as indicated by a dot and dash lineYdesignated by reference numeral I I2, and that the fulcrum member53 isadjusted to provide for such movement.

After the motor is adjusted as above described, it will then beconnected to the device (not shown) to be controlled. It will also beconnected ior control to an operators control valve or the like (notshown) which may be located at Va remote station and which may bemanually operative to vary the pressure of fluid in chamber 9 4betweenlimits such'as eighty and one hundred and fifty pounds, above mentioned.

Operation, Fig. 1

lWith fluidat the minimum ornormal pressure of eighty pounds present inpipe I3, all parts of the fluid motor will assumefthe positions in whichthey are shown in Fig. l `of the drawings as will be evident from theabove description.

Ii the operator now desires to rock lever 48 out of` its normal position.in a clockwise direction as viewed in the drawings, vhe will increasethe pressure of fluid in pipe i3 by an amount corresponding to thedesired extent of such movement. This increase in pressure beingeffective in chamber S on diaphragm 'l will deflect said diaphragmagainst the opposing-pressure of spring 'I'I to a position in which thepressure of said spring becomes increased to adegree which balances thepressure of fluid in'chamber 9 Vand in which position deflection of thediaphragm will cease.

This deflection of diaphragm I against the opposing pressure ofspring'l'l will act throughthe head-99 oi'sleeve 98 to movesai'dsleeve'into the valve member 85, and with the release valve |06 9normally seated, this movement will act through said valve to open thesupply valve 96.

When the supply valve 96 is opened, fluid under pressure supplied fromthe supply pipe I3 to the supply valve chamber 90, will flow past saidvalve and through ports les and 89 to chamber 23 at the right hand faceof the piston head 20 to increase the pressure in said chamber over thenormal pressure therein. When the pressure of fluid in chamber 23 isthus sufficiently increased with respect to the opposing pressure offluid in dash-pot chamber 21, piston means i9 Will move in the directionof the left hand and thereby rock lever 43 in a clockwise direction outof its normal position.

The piston means I9 may start moving, as just described, before thediaphragm 'l obtains the position in which it stops. After movement ofthe diaphragm 'l ceases however, the continued movement of piston meansI9 and valve member 85 will be relative to the supply valve 96 untilsaid member contacts the supply valve and prevents further supply offluid under pressure to chamber 23, whereupon movement of the pistonmeans I9 will promptly cease for reasons which will hereinafter bedescribed. v

If the operator now desires to move the lever d3 further in a clockwisedirection from normal position, he will increase the pressure of fluidin pipe l 3 by an amount corresponding to the degree of desiredmovement, and the motor will again operate as above described to rocklever 48 to the desired position. The pressure of fluid in pipe I3 maythus be increased in any desired increments, up to the maximum degree ofone I hundred fifty pounds, or it may be increased in a single orcontinuous step to the maximum pressure, and the motor willcorrespondingly operate to position lever said lever being moved to theposition indicated by the dot and dash line H2 when the maximum pressureof one hundred fifty pounds is provided in the control pipe i3.

From the above described operation it will be seen that the diaphragm 1,the release valve |06 and the supply valve 96, which constitute thepilot portion of the motor, are positioned directly by and in accordancewith the increase in pressure of fluid in pipe I3, Whereas the pistonmeans I9, constituting the power portion oi` the motor, is positioned inaccordance with the position of the diaphragm 1.

The movement of piston means I9 to any selected position may require anincrease in pressure of fluid in chamber 23 greater or less than theincrease in pressure in pipe I3, depending,Y

mainly upon the resistance to movement of the device being controlled.The pipe I3 being provided with fluid under pressure in excess of eightypounds, depending upon the increase in such pressure over the normaldegree for controlling the motor, constitutes a source of fiuid at apressure suiiciently in excess of the normal pressure of around fortypounds in chamber 23 to ensure obtaining adequate force on the pistonmeans I9 for operating a device having a maximum degree or resistance tomovement, as will be apparent.

As above mentioned, the piston means I9 will move to and stop in aposition corresponding to the pressure of fluid in chamber 9 and hencecorresponding to the position of diaphragm 1, it being noted that thisstopping occurs at the instant of closure of the supply valve 95. Thereason for this positive stopping of said piston means in a positioncorresponding to the position of said diaphragm will now be described.

As before mentioned, the dash-pot chamber 21 is at all times connectedto the supply pipe I3 so that the pressure of uid in said chamber willtend to increase through choke 28a, along with an increase in pressureof fluid in pipe I3, to provide an increase in the force which opposesmovement of the piston means I9 by the increase in pressure of uid inchamber 23. As soon as the piston means I 9 starts to move in responseto the increase in pressure of fluid in chamber 23, it will be notedthat the piston head 29 reduces the volume of chamber 21 and tends toincrease the pressure of uid in said chamber over the supply pipepressure effective in passage 26, so as to cause an outflow of fluidunder pressure from chamber 21 to said passage. Further, the rate ofsupply of fluid under pressure to and thus the rate of increase inpressure of uid in chamber 23 is limited by the ow capacity of the smallport or choke 89.

If the piston means I9 starts to move upon a relatively small increasein pressure of uid in chamber 23 under which condition the pressure ofuid in the dash-pot chamber 21 may not increase to any great degree overthe supply pressure in pipe I 3, it has been found that said pistonmeans will positively stop immediately upon closing of the supply valvedue apparently to the combination of factors including the high pressuredash-pot 21 above mentioned. In case however the piston means I9 tendsto move suddenly upon an increase in pressure of iiuid in chamber 23,due for instance to requiring a relative high force for initiatingmovement of the device being controlled, or for any other reason, thechoke 28a acts to so limit outow of iiuid under pressure from chamber21, that the piston head 29 will cause the pressure of fluid in saidchamber to increase over the supply pressure effective in passage 29 toa degree which will vary in proportion to the rate of such movement, andthis increase in pressure in chamber 21 will promptly decelerate or snubthe piston means I9 and prevent it over traveling the position in whichit is desired it will stop, so that when said position is attained andthe supply valve 95 closes, the piston means I9 will positively stop.Promptly upon stopping of the piston means i9 the pressure of i'luid inthe dash-pot chamber 21 will equalize through choke 28a with that in thesupply pipe.

Now assuming that the lever 48 has been moved to the position indicatedby the dot and dash line II2, or to any other position out of normalposition, if the operator desires to return .said lever toward itsnormal position, in which 1t is shown in the drawings, he will reducethe pressure of fluid in pipe I3 to a degree corresponding to thedesired new position of said lever.

Upon this reduction in pressure in pipe the diaphragm 1 will bedeiiected by spring 11 1n the direction of cover `5 to a positioncorrespondmg to the reduced, pressure. This deflection of diaphragm 1will be relative to the piston means I9 and thevalve member 85, andspring IIlI w1ll maintain the head 99 of sleeve 99 in contact with thediaphragm boss 89 and thus pull said sleeve out of contact with therelease valve |06. Fluid under pressure will then be released fromchamber 23 past the release valve |96 to bore I93 1n said sleeve andthence through the restricted release port or choke |94 to chamber 4 andthe release pipe 8. l

4When the pressure of uid in pipe I3 is reduced to effect a reduction ofpressure in piston chamber 23 as just described, the pressure in chamber21'betweenthe piston heads 291 and. 2| will start to reduce throughchoke 28a, but vas soon as the pressure in chamber 23 is reducedsufciently with respectto the pressure in chamber 21" to produce a forceon piston means I9 adequate to move said piston means in the directionof the right hand, said piston means will move and draw the lever 48back towards its normal position, in which it is shown in the drawingsAs the pistonmeans I 9 thus moves towards its normal position the volumeof dash-pot chamber 21'will increase and thereby tend to reduce thepressureof uid therein to a degree below the control pipe pressure inpassage 28. Thus upon initiating. thereduction in pressure in thecontrol 'pipe I3 there maybe a ow of fluid under4 pressure out ofchamber 211 through choke 28a, butthis flow will be. only momentary andthen a reverse flow may occur. The flow capacity of choke 28a, is suchhowever that as the piston means I9Zmoves in response toa reductioninpressure in chamber 23, the pressure in .the dashpot chamber 21 willreduce below that in passage 28 a degree corresponding to the rateofsuch movement. Thus if the movement of` piston means I 9j tendsV to beYrapid the reduction in pressure in chamber 21 will be so great as topromptly snub and decelerate the piston means; whereas in caserthemovement is at a slowenrate, thesnubbing action will be of. a lessdegree. There. may be substantiallyV no snubbing action incase the rateof' movement of piston means I9 is. sufciently slow, as. willbeapparent.

Asthe piston means ,I9 thus moves towards.

the right hand in response to a reduction in pressure in the controlpipe I3 it may initiallymove.

with.the diaphragm 1 as said diaphragm moves to its ,new positiondetermined by the reduction in pressurein controlpipe I3. After thediaphragm obtains itsV new position however and stopsmoving, themovement of piston means I9 will` then be relativeto .said diaphragmandwil1.

thusjnove release valve lllunder the action of spring H9' holdingthesupply valve 95 seated, in the. direction of 'andffinally into contactwith its` seat in a position of the piston means'correspending to theposition of` the diaphragm; Whenithe release valve I 'closes asjust de;

scribed, further reductionin pressure-inchamber. i

23 is prevented, whereupon movement of the pis, ton. means I9 will stop,therebyV stopping the leven lliinaiposition corresponding tothe posi'-tion.of,diaphragm,1.and hence thek pressure in.

pipeY IQ.. The piston means I9 will positively stop upon closing oftherelease valve |96 as just described, dlle tothe dash-pot action providedby chamber. 2l" and choke 28a, and the controlled rate of release offluidl under pressure from chamber 23. bythe release choke IU4, as abovedescribed.Y

If the. pressure in t-hecontrol. pipe I3ls furtherA reduced-themotoriwill operate in the same manner` asjustdescribed to positivelymove lever;48

to. anewiposition, correspondingto the degree ofl reduction in Apressureorto the reduced pressure in pipe` i3;` The lever 48 may thusbe causedtoV returnwto any. desired p ositionbyy reducing. the` pressure of .pipeIS'Lto the desiredY degree, while in, casefthepressure in pipe I3 isreducedtoiits normal ,degreether piston ,means Y I9, and lever 48 willberetu-rned to their, normal. positions as Will be apparent.

The action of the .dash-,pot chamber 21, which is always charged withuidunder pressure; and.

thev cooperative. eifect of, choke.,28a,. and of the.

overtraveling a position, corresponding to the pressure of iluid in pipeI3,.or in other words,` the structure assures that the piston means will,posi'tively, stopand remain. in alselective. position and therebyfaccurately position lever- 48 accord-4 ing to the pressure of .iluidinpipe I3. Moreover, the dash-pot chamber 21and choke 28a permits thechokes 8S and |04 tobe of suchsizeasfto provide a changelin pressure inthepower cham-.1 ber 23 at a rate which in no way interfereswith thedesired rate of movement of` lever.48 from one position to anotherposition..

It is desired to further point out that the diaphragm 1 and the follower13 are connected-to the other movable parts of the motor, only by therubber boss 80, and due to the resiliency-and relatively small area ofthis contact the diaphragm and follower 13' are. substantially inafloating condition .and hence freely adjustable against or by the forceof. spring 11 relative to said-motor parts. Tiltingof the diaphragmmaytherefore be free andrelative tothevalve memberA 85 so as to prevent`binding of sleeve 98fwithin said member, or binding of the piston stemL-l4`within the wear bushing 33." The diaphragm is thusadjustable with amaximum degree of accuracy with respect to changes inpressure of iluidinpipe I3, vand the parts controlled by said diaphragm are likewisefreelyadjustable, thereby providingfor correspondingly accurate adjustment of.piston means I9 and lever 48 which are forced to assume positionscorresponding to the accurately adjusted position of the diaphragm.

When thevmotor is mountedonan internal combustion engine the vibrationoftheV engine will .ca11se,vibration` of thediaphragm within the,casingas-.it substantially floats on the end of' spring 11.` The.rubber boss .895 acts however tominimize. transfer of.such vibrationtothe sleeve 98,"and.this.isivery important, in -that it will minimize.wear..y and. replacement of operating .parts of the structure associatedwith. thelpis ton means I9, and 'it will also prevent vibration of thevalvesontheirseats andconsequent leakage of; uidiunder. pressurepastsaidvalves.`

Incase of failure of the supply of fluid under` pressure Yon anairplane,byway of pipe` I3, it isdesirablelthat the different controlling.devices or motors on .the engine or engines automaticall'y. operateV toinsure Continued operation of the engine or engines .at an. adequatespeed to maintain the airplane in theair. The motor abovedescribed; andshown in Fig.- 1 of the drawings, may, be employedfor, controlling `therichness or temperature ofthe fuel mixture to an engine andin caseoflo'ss ofthe supply ofcontrolling uid'pressure to. pipe I3'it istherefore desirable thatthe. controlling.A lever 48 be automatically,movedback to its. normal .position to provideaa rich fuel mixture, orfuel ata tem.. perature` whichwill insure against freezing, of moisturein the fuel supply lines..

This automatic return of lever 48 to its normal position isobtainedinicase of.'loss of the supply of fiuid pressure to controlYpipe I3 and diaphragm chamber 9 by the force offspring'11; It'.will beseen that if the'pressureof .fluid in chamber 9 is lost, the spring |'Iwill move ange 'I5 on follower `|3 into contact with collar 95 on thevalve member 85, which will permit spring IDI to move sleeve 98 out ofContact with the release valve |04 so as to open chamber 23 toatmosphere, and spring 'I'I will then pull the piston means I9 to theposition in which the adjusting screw 68 engages the stop shoulder 59 onthe power cylinder portion I4, such contact being obtained prior to orat least coincidental with engagement between said diaphragm and stop 83in the cover 5.

Description and operation Fig. 2

The structure shown in Fig. 2 is particularly adapted for controllingthe throttle or speed of an engine such as above referred to, anddiffers from the structure shown in Fig. 1 mainly in the provision ofmeans for defining a, maximum pressure position of lever d8, and ofmeans for automatically positioning said lever intermediate its twoextreme positions in case of loss of the supply of controlling uid, soas to thereby maintain a supply of fue! to the engine which will ensureoperation of the engine at a speed sufficient to maintain the airplanein iiight.

By referring to my copending application, herebefore referred to, itwill be found that I have provided means whereby the pilot of the planeis able to adjust the speed of the several engines in unison, while theengineer is able to adjust the speed of the engines individually, sothat if all engines are not operating in synchronism in response to thepilots control, the engineer may adjust the speed of any individualengine or engines to obtain such synchronism. Now in case the pilot hadoperated his control device to provide for maximum engine speed, itwould be undesirable for the engineer to be able to effect an adjustmentto increase the speed of any individual engine, since such an adjustmentcould result in the breakage of links, etc.

Referring now to the structure shown in Fig. 2 wherein parts likecorresponding parts of the motor shown in Fig. l of the drawings, aredesignated by the same reference numerals.

The lever 43 is shown in the minimum engine speed or idling position,and the maximum engine speed position may be such as indicated by a dotand dash line H3. The boss d5 projecting into chamber 25 in the powercylinder position I4 of the motor is provided externally with screwthreads upon which is adjustably mounted a. stop H4, the inner end ofwhich stop is arranged for contact by piston means I9 when the lever 48is in its maximum speed position indicated by the dot and dash line H3.This adjustable stop IIA will be adjusted at the motor on all engines onthe plane to cause operation of the engines at the same maximum speeds.Thus, if the pilot adjusts the motors to obtain maximum speed of theengines, the engines will operate at maximum speed in synchronsm, andthe stops I I4 in the motors will prevent the engineer from adjustingthe motor in the direction to cause an increased speed and thus preventdamage to links or the like which may be used to connect the motors tothe fuel governing means on the engines.

The mean operative in case of failure of the supply of fluid underpressure to pipe I3 to movel tion IIB is employed in place of casingsection I and differs therefrom in not being provided with the end wall2 which carries sleeve 3. Interposed between the casing section l l 6and the power cylinder portion I4 of the motor is a casing section H'Ihaving an end wall |53 carrying centrally a sleeve like projection l I9,said end Wall and projection corresponding to the wall 2 and sleeve 3 inthe structure shown in Fig. 1, except that the outer surface ofprojection H9 is cylindrical in form and constitutes one wall of anannular ring-like piston chamber, the other concentric wall of which isprovided on the inner surface of the casing section ||'I. Disposedbetween these walls is an annular ring-like piston |29 having inner andouter ring grooves in which are mounted packing rings |2| and |22 havingsealing and sliding contact with the respective cylinder walls.

The regulating spring Il bears against one side of piston 29 while atthe opposite side of this piston there is a pressure chamber |23 betweenthe piston and end wall H8. Chamber |23 is connected by a passage |24 toa passage |25 which leads to one end of pipe 33 normally supplied withuid under pressure from the control pipe I3. Passage |24 also providescommunication between pipe 33 and passage 29 in the power cylinderportion I4 of the motor to supply fluid under pressure to the latter, asin the structure shown in Fig. l.

When the control pipe i3 is supplied with fluid under pressure, thispressure will be effective in chamber 23 on piston |29, and the area ofsaid piston is such that this pressure will move said piston to and thenhold it in the position in which it is shown in the drawings and whichis dened by contact with the end of the casing section I6. In thisposition spring i? will be conditioned identically as by Contact withwall 2 in the structure shown in Fig. 1.

Upon failure of pressure of iiuid in pipe I 3 and thereby in chamber|23, the pressure of spring 'Il will move the piston |20 in thedirection of the left hand to a position which may be defined i byengagement with adjusting shims |23 supported by the end wall i I8.

The piston means I9 has a stern |21 differing from stem 34 in thestructure shown in Fig. 1 of the drawings only in that an annularshoulder 28 is provided adjacent to and just back from the end engagedby collar 83 on the valve member 85. The piston |29 has a sleeve likeextension |29 projecting within spring TI and having adjacent its endsliding and supporting contact on the outer surface of the projection II9 car.- ried by wall HE. At the end of projection I ZS is an inturnedannular flange |33 provided for contact with shoulder |28 but slightlyspaced from said shoulder with the parts of the motor in their normalpositions in which they are shown in Fig. 2 of the drawings.

A cover |34 is used with this motor, instead of cover 5, and carriescentrally an adjustable stop` l 32 which extends into diaphragm chamberSand` which has screw-threaded engagement with said cover for movementeither toward or away from the diaphragm. A sealing ring |33 carried bycover l3| and engaging the peripheral surface of stop |32 is provided toprevent leakage of iiuid under pressure from chamber 9. A lock nut I 3.4on stop |32 is provided for contact with the cover to secure said stopin an adjusted position. The stop |32 is adjusted to a position in whichit is shown in the drawings and in this position the -diaphragm will beout of contact with said stopl when subjectpto'the normal controlpipepressure of 80 pounds: Upon failure ,of this pressure theA diaphragmwill be moved by spring .l'l'into con# tact with stop |32.

The valve member 35 is provided with a head |35,v differing from headall in the structure shown* in Fig, l, only in that collar 95iis omittedand a stop shoulder |35 is provided for contact with the diaphragmfollower flange 15'.

In operation, when the control pipe |3- is charged with iiuid at normalpressurey the parts of the motor shown in Fig. 2 will assume thepositions'in which they areshown in the drawings, and when sopositioned, said motor will operate in responseto rvarious pressures offluid in said pipe,-,above the normal pressure, in the same man-ner asthe structure shown in Fig. l, and above described.

However in case of failure' of the supply of vfluid under pressure topipe |3- the spring '|1'will move the piston |20 into contact with shims|26 and, at the same time, will move the diaphragm` 1 into contact withstop |32.

In casev theengine is operating at a speedin excess of that providedwith lever 4B in the position indicated by dot and dash line ||5 at thetime of failure of the supply of fluid under pressure to pipe 43,- theflange on the diaphragm fol1ower13 will contact shoulder |36 on thevalve member 85 and the spring 11, acting through said follower, willthen pull the piston means |9 and `lever 48 to the intermediate speedposition, indicated bythe dot and dashA line H5, in which position thediaphragm will contact stop |32.

At `the same timey the movement of piston |29- by spring.11 will moveflange |30 toward and into contact with shoulder |28 on the piston stem|21, said ,contact being obtained with the diaphragm 1 in contact withstop |32 and with said piston engaging shims |26, thereby securing thelever 48 against movement past the intermediate position in thedirection ofits normal position. The lever 48.will thus be securely heldby spring 11 in its mid-position, indicated by dot and dash line ||5against movement in one direction by contact between the follower flange15 and shoulder |36v on the valve member head |35, and in 'the oppositedirection by contact between the flange |3 on piston |20 and shoulder|28 on the piston stem |21.

Regardless of the position of lever 48 at the time of failure of fluidpressure in pipe |3, the structure. will operate to move lever 48' toand then hold it in its position indicated by dotand dash line H5, aswill be apparent withoutfurther description.

Summary From the above description it will now be seen that I haveprovided a fluid motor which is relatively small, compact, light inweight, sensitive to variations in control pressure, positive andaccurate in adjustment according to changes in the control pressure, andwhich is operative automatically in caseof failure of the supply ofcon-V trol pressure to automatically cause the device being controlledto assume a predetermined chosen position.

Having now described my invention. what I claim as new and desire tosecure by Letters Patent, is:

1. A fluid motor comprising a casing having a fluid pressure controlchamber and fluid pressure power chamber, power means in said'casingsub'- ject to and adjustable-in accordance with varia'- tions: inpressure in said power chamber, valve means :comprising :a v. movablemember operable.

uponiaxial ymovementin one direction to supply fluidrlunder pressure tosaidpower chamber and uponrmovementzin the' opposite direction torelease fluid under-pressure from said power chamber, pilot means insaid casing comprising a, flexibleidiaphragmarranged in coaxial relationwith said movable member,v` and a resilient boss associatedwith saidvdiaphragm 'at its center for contact `with saidsmovable member andcapable ofA movement tout `of Such contact, said pilotmeans beingsubjectto pressure of fluid in said control chamber and operable throughsaid boss upon an increase in such pressure to move said movable memberin said one direction, and means operable upon a reduction in pressureof fluid in said control chamber to move said movable member in theopposite direction.

2. A fiuid motor comprising a casing having a fluid pressure controlchamber and a fluid pressure power chamber, power means in said casingadjustable in accordance with variations in pressure of fluid in saidlpower chamber, valve means carried by said power means comprising amember movable axially of'said power means in one direction to effect asupply of fluid under pressure from a pressure chamber in said powermeans t0 said power chamber and movable axially of said power means inthe opposite direction to effect a release of fluid under pressure fromsaid power chamber, a eXible diaphragm in said casing arranged incoaxial relation with said movable member, an integrallyA formedresilient projection at the center of said diaphragm arranged to engagesaid movable member for moving said movable member in said one directionand capable of movement out of contact with said member, said diaphragmbeing subject to pressure of fluid in said control chamber and operableupon an increase in such pressure to move said movable member in saidone direction, and means operable upon a reduction in pressure of fluidin said control chamber to move said movable member in the oppositedirection.

3. A fluid motor comprising a casing having a fluid pressure controlchamber and a uid pressure power chamber, power means in said casingsubject to and adjustable by pressure of fluidin said power chamber,valve means operable to control pressure of'fluid in said power chamber,a regulating spring in said casing, pilot means in said casing subjectto pressure of said regulating spring and opposing pressure of fluid insaid control chamber and movable relative to said power means upon anincrease in pressure in said control chamber to effect operation of saidvalve means to supply iuid under pressure to said power chamber, saidregulating spring means being operable upon a reduction in pressure offluid in saidcontrolchamber to move said pilot means relative to saidpower means to effect operation of said valve means to release fluidunder pressure from said power chamber, and means providing for saidmovement of said pilot means relative to said power means and operableby said regulating spring means upon loss of fluid under pressure fromsaid control chamber to engage and move saidpower means to a chosenposition.

4. A fluid motor comprising a casing, apressure responsive power memberin said casing having a normal position and being movable therefrom uponsupply of fluid under pressure to a power chamber, valve means includinga valve control member operable uponfmovement in one direction to effectoperation of said valve means to supply fluid under pressure to saidchamber and upon movement in the opposite direction to effect operationof said valve means to release fluid under pressure from said chamber,pilot means in said casing arranged in coaxial relation to said valvemeans and valve control member and having a one-way drive connectionwith said valve control member and operable upon supply of fluid underpressure to a control chamber to effect movement of said valve controlmember in said one direction, regulating spring means in said casingopposing pressure of fluid on said pilot means and operable upon releaseof fluid under pressure from said control chamber to move said pilotmeans in a direction away from said valve control member, release meansoperable to move said valve control member in said opposite directionupon movement of said pilot means by said regulating spring, and meansoperable by said regulating spring to move said power member in thedirection of its normal position subsequent to operation of said valvemeans to release fluid under pressure from said power chamber.

5. A fluid motor comprising a casing having an interior wall, a powermember in said casing disposed at one side of said wall and cooperatingtherewith to form a power chamber, said power member having an extensionextending through said wall, supply and release valve means including anaxially movable control member carried by said extension in coaxialrelation therewith and being operable upon movement of said controlmember in the direction of said power member to supply uid underpressure to said power chamber and in the opposite direction to releasefluid under pressure from said power chamber, a release spring acting onsaid control member opposing movement thereof in the direction of saidpower member and operable to move said control member in said oppositedirection, a pressure regulating spring, pilot means in said casing ar-18 ulating spring, pilot means in said casing arranged in coaxialrelation to said control member and subject on one side to pressure ofsaid regulating spring and on the opposite side to pressure of fluid ina control chamber, pressure responsive means insaid casing operable bypressure of fluid in a third chamber to compress said regulating springagainst said pilot means, said pilot means being operable against saidregulating spring upon supply of fluid under pressure to said controlchamber to move said control'member in the direction of saidpower meansand being operable by said regulating spring upon release of fluid underpressure from said control chamber to render said release springeffective to move said control member in said opposite direction,

ranged in coaxial relation to said control member and subject on oneside to pressure of said regulating spring and on the opposite side topressure of fluid in a control chamber, and being operable against saidregulating spring upon supply of fluid under pressure to said controlchamber to move said control member in the direction of said powermember and being operable by said regulating spring upon release offluid under pressure from said control chamber to render said releasespring operable to move said control member in said opposite direction,and means operable by said regulating spring upon operation of saidcontrol member to release fluid under pressure from said power chamberto move said power member.

6. A fluid motor comprising a casing having an interior wall, a powermember in said casing disposed at one side of said wall and cooperatingtherewith to form a power chamber, said power member having an extensionextending through said wall, supply and release valve means including anaxially movable control member carried by said extension in coaxialrelation therewith and being operable upon movement of said controlmember in the direction of said power member to supply fluid underpressure to said power chamber and in the opposite direction to releasefluid under pressure from said power chamber, a release spring acting onsaid control member opposing movement thereof in the direction of saidpower member and operable to move said control member in said oppositedirection, a pressure regsaid pressure responsive means being movable bysaid regulating spring to a certain position upon loss of fluid underpressure from said third chamber, means operable by said pressureresponsive means upon movement to said certain position to urge saidpower means in a direction to a chosen position, and means operable bysaid regulating spring upon loss of fluid under pressure from saidcontrol Chamber and subsequent to operation of said control member torelease fluid under pressure from said power chamber to urge said powermember in the opposite direction to said chosen position.

7. A fluid motor comprising a casing having a power chamber, a controlchamber, a dash-pot chamber and a constantly open communication betweensaid control and dash-pot chambers, choke means said communicationadapted-*to restrict flow of fluid under pressure into and out of saiddash-pot chamber, a combined control and fluid pressure supply pipeconnected to said control chamber and normally charged with fluid at apressure in excess of atmospheric pressure, differential area movablepower means in said casing having at one side a relatively large areasubject to pressure of fluid in said power chamber and having at theopposite side a smaller area subject to pressure of iiuid in saiddash-pot chamber, pilot means in said casing subject to pressure of iuidin said control chamber, valve means in said casing for controlling thepressure of fluid in said power chamber, means connecting said valvemeans for control to both said pilot and power means, said pilot meansbeing movable relative to said power means upon an increase in pressureof fluid in said control chamber to effect operation of said valve meansto supply fluid under pressure from said pipe to said power chamber andupon a reduction in pressure of fluid in said control chamber to effectoperation of said valve means to release. fluid under pressure from saidpower chamber, said power means being movable in one direction bypressure of fluid in said power chamber upon supply of fluid underpressure thereto and being movable in the opposite direction by pressureof fluid in said dash-pot chamber upon release of fiuid under pressurefrom said power chamber, and being movable relative to said pilot meansupon cessation of movement of said pilot means, said power means beingoperable upon movement relative to said pilot means to eifect operationof said valve means to bottle the fluid pressure in said power chamberin a position of said power means corresponding to the position of saidpilot means.

8. A fluid motor comprising a casing, a combined control and fluidpressure supply pipe connected to said casing and normally charged within said power chamber and asmaller'area 'sub ject to pressure of fluidin said dash-pot chamber acting in opposition to pressure of`fluidinsaid power chamber, and means operableupon-an increase in pressure offluid in said pipe'to supply fluid yunder pressure from said pipeto'said power chamber and upon a reduction in` pressure of fluid in saidpipe to release fluid underpressure from said power chamber. Y

9. A fluid motor comprising a casing having a power chamber, a controlchamber and also having a third chamber which is constantly open to asource of fluid under pressurapowermeans in said casing having arelatively 'large area subject to pressure of uid in'said power chamberr'and a smaller 'area-subject `to opposing vpressure of Viiuid in saidthird chamber, Vvalve mea'ris'in said-.casing operable tocontrolpressure'of Afluid infsaidpower chamber, regulating springmeans insaidlcasing, pilot means in said casing subject to pressure of fluid in said`controlvchamberand opposing pressure of said spring means and mov- Yablerelative to said powervmeans upon an in c'reasein pressure in saidcontrol chamber to 'effect operation of said 'valvemeans to fsupplyfluid under pressure'to said power chamber and movable by said springmeans relative to Asaid power means 'upon a reduction-in pressure insaid control chamber to/eiect operation of said valve means to'releaseiiuid under pre'ssurefrom said power chamber, 'means 4arranged to limitthe lexterit of movement of said pilot means by'said regulatingspringmeans vrelative to 'said valve means upo'n Aa reduction A'n pressure of'fluid in said control chambe'rand operableV by said spring means uponloss of fluid under Vpressure lfrom said'control chamber to move saidpower means to a chosen position.

VRANKIN J. BUSH.

